1. Field of the Invention
The present invention is directed to a semiconductor chip for optoelectronics of the type having an active layer with a photon-emitting zone and that is attached to a carrier member at a bonding side.
2. Description of the Prior Art
Semiconductor chips of the above type produced in thin-film technology are disclosed in European Application 0 905 797. For manufacturing the known semiconductor chip, an active layer is usually applied on a substrate with an epitaxial process. A carrier member is subsequently secured to the upper side of the active layer, and the substrate is removed. A metallic reflection layer is located between the carrier member and the active layer, so that no light is absorbed by the carrier member. The known semiconductor chips are particularly suitable for applications wherein a high optical power is required.
One disadvantage of the known semiconductor chips manufactured in thin film technology is that the metallic reflection layer arranged between the carrier member and the active layer generally does not exhibit a satisfactory reflectivity at short wavelengths. Particularly given a wavelength of less than 600 nm, gold becomes increasingly inefficient as the metallic reflection layer, since the reflectivity significantly decreases. At wavelengths below 600 nm, for example, the elements Al and Ag can be employed, their reflectivity remaining comparatively constant at wavelengths below 600 nm.
Moreover, large surfaces such as the metallic reflection layer are difficult to bond. As a result of the bonding and the alloying of the metallic contact layer, moreover, the quality of the metallic reflection layer is generally degraded.
German OS 198 07 758 discloses a truncated pyramid-shaped semiconductor chip that has an active, light-emitting zone between an upper window layer and a lower window layer. The upper window layer and the lower window layer together form a truncated pyramidal base member. The slanting alignment of the sidewalls of the window layers cause the light emanating from the active zone to be totally reflected at the side faces, so the reflected light is incident on the base area of the truncated pyramid-shaped base member, serving as luminous surface, substantially at a right angle. As a result, a part of the light emitted by the active zone emerges onto the surface within the exit cone of the semiconductor element. The term exit cone in this context means the cone of the light rays whose incident angle is smaller than the critical angle for the total reflection and that are therefore not totally reflected. In order to arrive at a significant enhancement of the light yield, this concept assumes a minimum thickness for the upper and lower window layer. In the known truncated pyramid-shaped semiconductor component, the thickness of the upper and lower window layer amounts to at least 50.8 μm (2 milli-inches). Such a thickness is still within a range allowing the layers to be produced without difficulty. If, however, the power of the known semiconductor chip is to be increased, it is necessary to scale all dimensions. Layer thicknesses thereby quickly derive that can be manufactured only given high outlay in an epitaxial layer. The known semiconductor chip is therefore not scalable without further difficulty.